In order to interact effectively with the world, people depend on information about the spatial locations of objects in their immediate environment. A thorough understanding of the brain mechanism and mental, processes that underlie spatial orientation will have important implications for a wide range of behaviors, and may ultimately facilitate the design of prosthetic and robotic devices, and the diagnosis and treatment of movement disorders related to mental health. The research proposed herein is directly concerned with contributing toward such an understanding. The specific objectives are to learn more about the different types of spatial information that people may use to locate a seen object, and how that information is involved in guiding movements of the eyes and limbs. To study these questions, three series of experiments will be conducted in which subjects will produce eye and limb movements to visual stimuli under a variety of different stimulus conditions, and using a variety of different types of responses. In the first series of experiments a new analytic technique will be used to evaluate kinematic features of rapid aimed limb movements. These experiments will explore the possibility that spatial information is used differently during different component phases of a single rapid movement as a function of the types of eye movements that subjects produce, the patterns of retinal stimulation they receive, the nature of the spatial information that must be retained in memory, and the physical dimensions of the movements. The second series of experiments will explore some of the factors involved in the use of spatial information to guide unspeeded limb movements. These experiments focus on learning more about the various different types of spatial information that are available for movement control. The final series of experiments extends the endeavor to saccadic eye movements, and directly compares the use of spatial information by the eye and hand. These experiments will examine kinematic features of eye movement trajectories to determine the extent to which eye and limb motor systems share the same spatial representations. Results of the proposed experiments should lead to new insights into the fundamental processes underlying various aspects of perception, cognition, and action that are relevant to spatially criented behavior. With these insights, it should be possible to better diagnose, treat, and prevent serious movement disorders related to mental health.